Siemens Fault 0a7991 Fix Info

A: No. In the vast majority of cases, A7991 is purely a procedural notification and indicates no hardware defect.

Run a short ramp. If speed remains near zero while torque climbs to p2175 , the fault is legitimate – mechanical block.

In essence, the drive commands the motor to accelerate to a target speed. The internal speed encoder (or sensorless vector control) reports back the actual speed. If the actual speed remains significantly below the target speed for a defined period (set by parameter p2178 ), the drive assumes the motor is mechanically blocked and trips.

For a deep dive into the technical details of the identification process itself, you should refer to the section of the SINAMICS G120 List Manual or the operating instructions for your specific drive model (e.g., G120, S120, or G130).

: This fault triggers when the motor cannot move as expected or reaches its torque/current limit for too long. siemens fault 0a7991

: Ensure the Profinet/Profibus cable is securely plugged in and the PLC is powered on.

When you encounter F07991 on a Siemens SINAMICS panel or Starter/TIA Portal, follow this structured diagnosis.

According to official Siemens documentation, A07991 (Alarm A7991) appears when the drive is set to activate this motor data detection function. While it is an alarm with the letter "A" prefix, it is important to note that it is merely a notification and can be safely resolved without causing immediate damage to the drive or motor.

The motor data identification has not been completed, and the drive has not received the command to stop the ID run process. Step-by-Step Solution: How to Fix A07991 If speed remains near zero while torque climbs

The alarm is primarily triggered on Siemens SINAMICS drives (including the series) by three specific actions:

For modular drives (like the S120):

Specifically, points to an issue with I/O access errors or parameter assignment errors on a distributed I/O system—most commonly associated with PROFIBUS or PROFINET networks. The fault indicates that the CPU has detected a discrepancy between the configured hardware and the actual physical hardware, or that an I/O module is reporting a channel-specific error.

“Configure the drive with the basic settings, the drive will do the 'auto tune' at the first 'run' command, wait for that to finish, the motor whistling for a bit and then go quiet. Re make the run command, the fault should go away.” Siemens SiePortal If the actual speed remains significantly below the

The fault code 0A7991 is a specific error code generated by Siemens systems to indicate a particular problem. While the exact meaning of this code can vary depending on the specific Siemens product or system it appears in, a general approach to understanding and troubleshooting such faults will be discussed.

The Siemens alarm code (or A07991 ) specifically indicates that "Motor data identification is activated" . While there isn't a single formal academic "paper" on this specific routine, it is a standard commissioning procedure documented extensively in Siemens technical manuals and support forums. Summary of Fault A7991

: While this alarm is active—especially if a rotating measurement is selected—you may be unable to save parameter assignments to the ROM until the process finishes. Common Troubleshooting Steps

When a sensor or actuator cable is shorted to ground or to 24V, the I/O module may detect an overcurrent condition. Some modules go into "fault" state and report via diagnostic interrupt 0A7991.

Experts on the Siemens SiePortal Forum often suggest specific sequences for persistent alarms:

Set (Motor data identification and rotation test: Disabled).